Preserving sorbent devices in dialysis systems

ABSTRACT

A method of preserving a sorbent device of a dialysis system, the method comprising—after administering a first dialysis treatment at the dialysis system and before administering a second dialysis treatment at the dialysis system—circulating a fluid through the sorbent device to prevent matter within the sorbent device from solidifying and circulating the fluid through a filter coupled to an outlet of the sorbent device to remove contaminants from the fluid.

TECHNICAL FIELD

This disclosure relates to fluid conditioning systems for generating andconditioning dialysis fluid utilized by dialysis machines to carry outdialysis treatments. Such fluid conditioning systems can includecomponents and configurations for prolonging a usage life of a sorbentcartridge.

BACKGROUND

Dialysis is a medical treatment that provides life-saving support topatients with insufficient renal function. The two principal dialysismethods are hemodialysis (HD) and peritoneal dialysis (PD). During HD,the patient's blood is passed through a dialyzer of a dialysis machine,while a dialysis solution (or, dialysate) is also passed through thedialyzer, generally in an opposite or countercurrent direction. Asemi-permeable membrane within the dialyzer separates the blood from thedialysate and allows fluid exchanges to take place between the dialysateand the blood stream via diffusion, osmosis, and convective flow. Theseexchanges across the membrane result in the removal of waste products(e.g., such as solutes, like urea and creatinine) from the blood. Theseexchanges also help regulate the levels of other substances (e.g.,sodium and water) in the blood. In this way, the dialyzer and dialysismachine act as an artificial kidney for cleansing the blood.

During PD, the patient's peritoneal cavity is periodically infused withdialysate. The membranous lining of the patient's peritoneum acts as anatural semi-permeable membrane that allows diffusion and osmosisexchanges to take place between the solution within the peritonealcavity and the blood stream. Like HD, these exchanges across thepatient's peritoneum result in the removal of waste products from theblood and help regulate the levels of other substances (e.g., sodium andwater) in the blood.

Some dialysis systems also include a sorbent cartridge for regenerating(e.g., recycling) dialysate, which substantially reduces the amount ofdialysate needed to effect a complete treatment session. However, thecapability of the sorbent cartridge to regenerate dialysate candeteriorate once a dialysis treatment has been completed and fluid nolonger circulates through the sorbent cartridge.

SUMMARY

This disclosure relates to fluid conditioning systems for generating andconditioning dialysis fluid utilized by dialysis machines to carry outdialysis treatments.

In some embodiments, a fluid conditioning system includes components andconfigurations for prolonging a usage life of a sorbent cartridge.

In one aspect, a method of preserving a sorbent device of a dialysissystem includes—after administering a first dialysis treatment at thedialysis system and before administering a second dialysis treatment atthe dialysis system—circulating a fluid through the sorbent device toprevent matter within the sorbent device from solidifying andcirculating the fluid through a filter coupled to an outlet of thesorbent device to remove contaminants from the fluid.

Embodiments may include one or more of the following features.

In some embodiments, the method further includes circulating the fluidthrough the sorbent device and through the filter for a period of about24 hours to about 72 hours.

In some embodiments, the fluid is unheated.

In some embodiments, the fluid has a room temperature of about 15° C. toabout 25° C. while the fluid is circulated.

In some embodiments, the method further includes circulating the fluidthrough the sorbent device and through the filter at a flow rate ofabout 50 mL/min to about 150 L/min.

In some embodiments, the method further includes circulating the fluidusing a pump positioned downstream of the filter.

In some embodiments, the method further includes powering the pump witha power supply.

In some embodiments, the power supply includes a backup battery.

In some embodiments, the method further includes regenerating spentdialysate using the sorbent device during the first dialysis treatmentand during a predetermined number of one or more additional dialysistreatments.

In some embodiments, the method further includes monitoring a usage lifeof the sorbent device at a timer of the dialysis system.

In some embodiments, the method further includes determining that thesorbent device is exhausted and preventing the dialysis system fromoperating after determining that the sorbent device is exhausted.

In some embodiments, the sorbent device and the filter are configured tobe replaced at the dialysis system respectively with a new sorbentdevice and a new filter.

In some embodiments, the method further includes preventing dialysatefrom becoming stagnant within the sorbent device.

In some embodiments, the filter is an ultrapure filter.

In some embodiments, the filter is disposed adjacent the sorbent device.

In some embodiments, the filter is disposed atop the sorbent device.

In some embodiments, the method further includes administering thesecond dialysis treatment at the dialysis system.

In some embodiments, the method further includes—after administering thesecond dialysis treatment at the dialysis system and beforeadministering a third dialysis treatment at the dialysissystem—circulating a fluid through the sorbent device to prevent matterwithin the sorbent device from solidifying and circulating the fluidthrough the filter to remove contaminants from the fluid.

In some embodiments, the contaminants include one or both of bacteriaand endotoxins.

In some embodiments, the fluid includes water.

In another aspect, a dialysis system includes a sorbent devicepositioned along a fluid circuit for regenerating dialysate during adialysis treatment carried out at the dialysis system, a filter coupledto an outlet of the sorbent device such the any fluid flowing throughthe sorbent device must first flow through the filter before reenteringthe fluid circuit, and a pump positioned downstream of the filter alongthe fluid circuit. The pump is operable between first and seconddialysis treatments carried out at the dialysis system to circulate afluid through the sorbent device to prevent matter within the sorbentdevice from solidifying and circulate the fluid through the filter toremove contaminants from the fluid.

Embodiments may include one or more of the following features.

In some embodiments, the dialysis system further includes a dialyzer andthe fluid circuit, wherein the fluid circuit is configured forcirculation of the dialysate along one side the dialyzer during thedialysis treatment.

In some embodiments, the dialysis system further includes a controlsystem configured to operate the pump.

In some embodiments, the pump is operable to circulate the fluid throughthe sorbent device and through the filter at a flow rate of about 50mL/min to about 150 mL/min.

In some embodiments, the dialysis system further includes a reusablepower supply positioned along the fluid circuit and configured to powerthe pump.

In some embodiments, the reusable power supply includes a backupbattery.

In some embodiments, the sorbent device is configured to be used duringmultiple dialysis treatments until the sorbent device has beenexhausted.

In some embodiments, the dialysis system further includes a timer formonitoring a usage life of the sorbent device and a control system bywhich the timer is implemented.

In some embodiments, the control system is configured to determine thatthe sorbent device is exhausted and prevent the dialysis system fromoperating after determining that the sorbent device is exhausted.

In some embodiments, the filter is an ultrapure filter.

In some embodiments, the filter is disposed adjacent the sorbent device.

In some embodiments, the filter is disposed atop the sorbent device.

Embodiments may provide one or more of the following advantages.

Damage to functional layers of the sorbent cartridge may be avoided bycontinuously circulating fluid through the fluid circuit betweendialysis treatments as part of a sorbent preservation cycle. Continuousfluid flow through the sorbent cartridge prevents the chemical layers ofthe sorbent cartridge from solidifying after initial wetting.Furthermore, any small amounts of contaminants that may have beenintroduced into the fluid at the sorbent cartridge are trapped at thefilter and thereby removed from the fluid as the fluid flows through thefilter. In this manner, the circulating fluid is cleaned by the filteras the fluid flows through the fluid circuit. The filter has a lightweight and a small size that only marginally increase an overallfootprint of the sorbent cartridge. Circulating fluid through the filterduring the sorbent preservation cycle can extend the life of the sorbentcartridge for use during multiple dialysis treatment cycles over severalweeks, thereby avoiding costs and efforts that would otherwise beassociated with discarding and replacing a sorbent cartridge each time adialysis treatment cycle would be performed during that time period.

Other aspects, features, and advantages will be apparent from thedescription, the drawings, and the claims herein.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a fluid conditioning system that cancooperate with a dialysis system to carry out a fluid conditioning cyclethat includes a dialysis treatment.

FIG. 2 is a top view of the fluid conditioning system of FIG. 1 .

FIG. 3 is a front view of the fluid conditioning system of FIG. 1 .

FIG. 4 is a rear view of the fluid conditioning system of FIG. 1 .

FIG. 5 is a rear view of the fluid conditioning system of FIG. 1 , withcertain exterior components omitted to expose certain interiorcomponents.

FIG. 6 is a perspective view of the fluid conditioning system of FIG. 1, with certain exterior components omitted to expose certain interiorcomponents.

FIG. 7 is a perspective view of the fluid conditioning system of FIG. 1, with certain exterior components omitted to expose certain interiorcomponents.

FIG. 8 is a perspective view of the fluid conditioning system of FIG. 1, with certain exterior components omitted to expose certain interiorcomponents.

FIG. 9 is a perspective view of a front assembly of the fluidconditioning system of FIG. 1 .

FIG. 10 is a rear perspective view of the front assembly of FIG. 9 .

FIG. 11 is a rear perspective view of the front assembly of FIG. 9 .

FIG. 12 is a rear perspective view of a heater bag of a door assembly ofthe front assembly of FIG. 9 .

FIG. 13 is a rear perspective view of a heater plate of a door assemblyof the front assembly of FIG. 9 .

FIG. 14 is a perspective view illustrating installation of the heaterbag of FIG. 12 and a fluid cassette of the fluid conditioning system ofFIG. 1 .

FIG. 15 is a perspective view of the fluid cassette of FIG. 14 , alongwith the heater bag of FIG. 12 .

FIG. 16 is a full exploded perspective view of an embodiment of a heaterassembly that may be included within the fluid conditioning system ofFIG. 1 .

FIG. 17 is a partially exploded perspective view of the heater assemblyof FIG. 16 .

FIG. 18 provides an operational diagram by which the fluid conditioningsystem of FIG. 1 can cooperate with a dialysis system to form a fluidcircuit for carrying out the fluid conditioning cycle.

FIG. 19 illustrates an example setup of the fluid conditioning system ofFIG. 1 with the dialysis system of FIG. 16 .

FIG. 20 illustrates a fluid flow path (indicated by highlighted fluidlines) of a priming stage of the fluid conditioning cycle carried outvia the fluid circuit of FIG. 16 .

FIG. 21 illustrates a fluid flow path (indicated by highlighted fluidlines) of an infusion stage of the fluid conditioning cycle carried outvia the fluid circuit of FIG. 16 .

FIG. 22 illustrates a fluid flow path (indicated by highlighted fluidlines) of a treatment stage of the fluid conditioning cycle carried outvia the fluid circuit of FIG. 16 .

FIG. 23 provides a block diagram of a control system of the fluidconditioning system of FIG. 1 .

FIG. 24 provides a block diagram of a hardware system of the fluidconditioning system of FIG. 1 .

FIG. 25 provides a block diagram of a software system of the fluidconditioning system of FIG. 1 .

FIG. 26 shows a portion of a sorbent system of the fluid conditioningsystem of FIG. 1 .

FIG. 27 is a schematic illustration of the sorbent system of FIG. 26 .

FIG. 28 is a cut-away view of a sorbent cartridge of the sorbent systemof FIG. 26 .

DETAILED DESCRIPTION

FIGS. 1-4 illustrate a fluid conditioning system 100 that can beoperated to prepare conditioned dialysate for use in a dialysis system.For example, the fluid conditioning system 100 can be fluidlycommunicated with the dialysis system to deliver “fresh” (e.g., cleaned,conditioned) dialysate to the dialysis system, collect “spent” (e.g.,contaminated, unconditioned) dialysate from the dialysis system, andregenerate (e.g., cleanse) and condition the spent dialysate in acontinuous fluid flow loop to recycle the spent dialysate. Exampledialysis systems with which the fluid conditioning system 100 can befluidly communicated include hemodialysis (HD) systems, peritonealdialysis (PD) systems, hemofiltration (HF), hemodiafiltration (HDF) andother related systems.

The fluid conditioning system 100 includes a housing 101 that containsor supports components of the fluid conditioning system 100, a fluidcassette 102 that includes multiple fluid lines defining various fluidpathways, two relatively high capacity pumps 103 that can circulatefluid within the fluid lines of the fluid cassette 102, and tworelatively low capacity pumps 104 that can deliver (e.g., infuse)conditioning agents into the fluid circulating within the fluid lines ofthe fluid cassette 102. The fluid conditioning system 100 has a compactfootprint that facilitates lifting and transport of the fluidconditioning system 100. For example, the fluid conditioning system 100typically has a length of about 30 cm to about 50 cm, a width of about30 cm to about 50 cm, a height of about 30 cm to about 50 cm, and aweight of about 15 kg to about 20 kg.

The housing 101 includes left and right side panels 105, 106, handles107 positioned along the side panels 105, 106 for carrying the fluidconditioning system 100, a door assembly 108 that can be opened andclosed to insert a heater bag, a front panel 109 to which the doorassembly 108 is secured, rear and bottom panels 110, 111 that furtherenclose the interior components, an upper panel 112 that supports thefluid cassette 102 and the pumps 103, 104, and a cover 113 that protectsthe fluid cassette 102 and the pumps 103, 104. Example materials fromwhich the exterior panels of the housing 101 may be made includeplastics, such as acrylonitrile butadiene styrene (ABS) andpolycarbonate blends, among others.

The cover 113 is typically made of ABS or polycarbonate and istransparent or translucent to allow visualization of the fluid cassette102 and the pumps 103, 104. The cover 113 can be pivoted at a rear hinge114 disposed along the upper panel 112 to open or close the cover 113.The upper panel 112 carries two latches 115 that can be closed upon afront edge 116 of the cover 113 to secure the cover 113 in a closedposition. The latches 115 can also be pulled up and apart from the cover113 to release the cover 113 from the closed position for accessing thefluid cassette 102 and the pumps 103, 104.

Referring to FIG. 5 , the fluid conditioning system 100 also includesleft and right side interior support frames 117, 118 to which the leftside, right side, front, rear, bottom, and upper panels 105, 106, 109,110, 111, 112 are attached. The interior support frames 117, 118 aretypically formed from sheet metal.

Each pump 103, 104 is a peristaltic pump that includes multiple rollerspositioned about the circumference of a rotatable frame (e.g., a motor)that carries a fluid line extending from the fluid cassette 102. As therotatable frame is rotated, the rolling members apply pressure to thefluid line, thereby forcing fluid to flow through the fluid line.

FIGS. 6-8 illustrate certain interior components of the fluidconditioning system 100. For example, the fluid conditioning system 100further includes multiple pressure transducers 119, two temperaturesensors 120, and an ammonia detector 121 that are respectivelypositioned within holes 122, 123, 124 in the upper panel 112 forengagement with the fluid cassette 102. The pressure transducers 119 areembodied as thin, flexible membranes that contact corresponding thin,flexible membranes 164 within the fluid cassette 102 (refer to FIG. 15 )for detecting fluid pressures within certain fluid pathways of the fluidcassette 102. The temperature sensors 120 are infrared (IR) sensors thatdetect temperatures of the dialysate flowing through certain points ofthe fluid pathways of the fluid cassette 102. The ammonia detector 121is a red-green-blue (RGB) color sensor that can detect color changes ona paper strip within the fluid cassette 102 for determining aconcentration of ammonium (e.g., which generates ammonia) within thedialysate flowing through a certain fluid pathway of the fluid cassette102. The fluid conditioning system 100 also includes circuitry thatacquires and conditions signals generated by conductivity sensors thatare provided on the fluid cassette 102, which will be discussed in moredetail below.

The fluid conditioning system 100 also includes multiple actuators 125that are aligned with holes 126 in the upper panel 112 for respectivelyand selectively moving multiple valves of the fluid cassette 102. Eachactuator 125 is mounted to a platform 127 of an internal frame 128 ofthe fluid conditioning system 100 and includes a motor 129 and a driveunit 130 that can be moved (e.g., rotated or otherwise manipulated) bythe motor 129. The drive unit 130 is equipped with a coupling member 131that is formed to engage a respective valve of the fluid cassette 102such that movement of the drive unit 130 produces movement of the valve.The internal frame 128 also includes columnar support members 132 thatsupport and locate the upper panel 112 of the housing 101. The upperpanel 112 further defines holes 133 that are positioned and sized toreceive locating pins 134 for appropriately positioning the fluidcassette 102 with respect to the upper panel 112. With the fluidcassette 102 in place, the locating pins 134 can be snapped down towardthe upper panel 112 to lock the position of the fluid cassette 102. Thefluid conditioning system 100 also includes a circuit board 135 equippedwith electronics for operating the various electromechanical componentsof the fluid conditioning system 100. For example, the electronicsexecute codes for carrying out the various stages of a fluidconditioning cycle (as discussed below with reference to FIGS. 18-20 ),operating the pumps 103, 104, turning valves for the fluid cassette 102,processing sensor signals, operating the actuators 125, operating aheater assembly 151, and running control loops (e.g., control loops forregulating dialysate temperature, regulating pump speeds to achievedesired flow rates, regulating pump speeds to achieve desired dialysatechemical compositions, and ensuring device safety).

Referring again to FIG. 5 , the fluid conditioning system 100 furtherincludes a support bracket 136 and a fan 137 carried therein for coolingthe circuit board 135 and other internal components of the fluidconditioning system 100. The fluid conditioning system 100 also includesa power supply 138, as well as a support bracket 139 that carries anA/C-in port 140.

FIGS. 9-13 illustrate various views of a front assembly 141 of the fluidconditioning system 100. The front assembly 141 includes the doorassembly 108 and the front panel 109 of the housing 101. The doorassembly 108 is pivotable at hinges 142 with respect to the front panel109 to allow loading of the heater bag 153 into the fluid conditioningsystem 100. The hinges 142 are friction hinges located along oppositesides of the door assembly 108, as shown in FIG. 12 .

The front panel 109 carries a latch assembly 143 that cooperates with abutton 144 carried by the upper panel 112 (shown in FIGS. 1-4 ) toreleasably secure the door assembly 108 to the front panel 109 in aclosed position. For example, depression of the button 144 adjusts thelatch assembly 143 so that the door assembly 108 can be unlocked from aclosed position and pivoted to an open position. The door assembly 108can alternatively be pivoted inward from an open configuration untiloppositely positioned screws 145 (e.g., shoulder screws, shown in FIG.12 ) engage the latch assembly 131 to lock the door assembly 108 in theclosed position. The latch assembly 131 has a contact switch fordetermining whether the door assembly 108 is open or closed. Referringparticularly to FIGS. 11 and 13 , the door assembly 108 includes anoptical switch 147 that indicates whether or not the heater bag isinserted. In some embodiments, the fluid conditioning system 100 may beinoperable when the door assembly 108 is open.

Referring particularly to FIG. 9 , the door assembly 108 supports adisplay screen 148 (e.g., a touchscreen display) on which graphical userinterfaces (GUIs) can be displayed and two control panels 149 that caneach be equipped with selectors 150 (e.g., buttons) for providing inputsat the GUIs to operate the fluid conditioning system 100. Exampleparameters and processes that may be controlled by a user via thedisplay screen 148 using the selectors 150 include starting and stoppinga treatment, initiating a drain cycle, changing a flowrate, initiating apriming stage of a fluid conditioning cycle, initiating systempreparation to start a fluid conditioning cycle, adjusting a temperatureaccording to patient comfort, confirming correct placement of the fluidcassette 102, or confirming correct placement of fluid lines thatinterface with the pumps 103, 104.

Referring to FIGS. 10-13 , the front assembly 141 includes components ofa heater assembly 151 that is designed to regulate fluid temperatures ofdialysate transported along the fluid pathways of the fluid cassette102. Referring particularly to FIG. 12 , the heater assembly 151includes a heater bag 153 that is equipped with an input connection 154and an output connection 155 that can interface with the fluid cassette102 for allowing dialysate to circulate through the heater bag 153 to bewarmed. The heater bag 153 is formed as a plastic channel that has agenerally flat, collapsed shape when empty, that inflates upon fillingwith fluid, and that transfers heat from an exterior surface todialysate flowing through the heater bag 153.

Referring particularly to FIG. 13 , the heater assembly 151 furtherincludes two plates 156 (e.g., aluminum plates) that position andsupport the heater bag 153 and that are heated for transferring heat tofluid within the heater bag 153. Referring particularly to FIG. 14 , theheater bag 153 can be slid between the two heater plates 156 (notvisible in FIG. 14 ) within the door assembly 108 when the door assembly108 is in the open configuration. Referring particularly to FIGS. 10-12, the heater assembly 151 further includes one or more heating elements(for example, resistive type heating elements that are not shown) bywhich fluid in the heater bag 153 can be warmed and two insulation pads158 disposed on opposite sides of the heater bag 153. The one or moreheating elements are carried by or otherwise attached to one or both ofthe plates. The heater assembly 151 also includes a circuit board 159that provides electronics for operating the heater assembly 151, a feedline 160 for each heating pad 156 that provides power, and thermocoupleconnections 162 for determining a temperature of the respective heatingplates 156.

FIGS. 15 and 16 illustrate another embodiment of a heater assembly 170that may be included in the fluid conditioning system 100 instead of theheater assembly 151. The heater assembly 170 is similar in constructionand function to the heater assembly 151 and accordingly includes theheater bag 153 sandwiched between the two heater plates 156. The heaterassembly 170 further includes two handles 171 attached to the heater bag153 for easy placement of the heater bag 153, a u-shaped heater frame172 that supports the heater bag 153, and two support members 173 of agenerally matrix construction that support the heater plates 156. Thesupport members 173 further serve to insulate the heater bag 153 and theheater plates 156 from surrounding components via air gaps 174 definedby the matrix construction that are disposed between the heater plates156 and such components.

Referring to FIG. 17 , the fluid cassette 102 is a single-use,disposable cartridge that includes a housing 200, multiple fluid lines201 arranged within the housing 200, multiple valves 202 positionedalong the fluid lines 201, two conductivity sensors 203 positioned alongthe fluid lines 201, an ammonia sensor 165 positioned along the fluidlines 201 for cooperation with the ammonia detector 121, two fluid lineconnectors (e.g., pump segment clips) 204, and two fluid line connectors(e.g., pump segment clips) 205. The fluid lines 201 cooperate with theheater bag 153 and a dialysis system to form a fluid circuit 350 forcarrying out a fluid conditioning cycle. For example, the fluid lines201 include ports to which the input and output connections 154, 155 ofthe heater bag 153 can be connected for providing fluid communicationbetween the fluid lines 201 and the heater bag 153. The fluid lineconnectors 204 locate fluid line segments 206 about the high-capacitypumps 103, and the fluid line connectors 205 locate fluid line segments207 about the low-capacity pumps 104. The fluid cassette 102 alsoincludes additional fluid lines that extend from the fluid cassette 102to various fluid containers, as illustrated in FIG. 19 .

The valves 202 are three-way valves by which two alternative fluidpathways can be selected by a control system of the fluid conditioningsystem 100. Lower portions of the valves 202 are formed to engage withthe coupling members 131 of the actuators 125 for movement of the valves202. Example types of valves 202 that may be included in the fluidcassette 102 include rotary valves, push-pull valves, sliding valves,and shuttle valves.

FIG. 18 illustrates an operational diagram 300 by which the fluidconditioning system 100 can cooperate with a dialyzer 337 of a dialysissystem 301 to form the fluid circuit 350 (indicated by solids lines) forcarrying out a fluid conditioning cycle, while FIG. 19 illustrates anexample setup of the fluid conditioning system 100 with the dialysissystem 301. Example types of dialysis systems 301 that may be coupled tothe fluid conditioning system 100 include HD systems, PD systems, HFsystems, and HDF systems. The fluid circuit 350 incorporates componentsof the fluid cassette 102, as well as various other components of thefluid conditioning system 100.

For example, in addition to the components discussed above with respectto FIGS. 1-17 , the fluid conditioning system 100 also includes acontrol system 161 (e.g., including the circuit boards 135, 159, as wellas additional circuit boards for sensor circuitry) for controllingvarious operations of the fluid conditioning system 100 and severalother, peripheral components positioned along the fluid circuit 350.These components include a prime tank 302 for collecting water toproduce dialysate (e.g., sometimes referred to as dialysis fluid), asorbent cartridge 303 for filtering tap water to provide purified watersuitable for creating dialysate and for cleansing dialysate exiting thedialysis system 301, a primary reservoir 304 for collecting fluid (e.g.,unconditioned water or dialysate) exiting the sorbent cartridge 303, asecondary reservoir 305 for collecting fluid that exceeds a capacity ofthe primary reservoir 304, a bag 306 for containing an electrolytesolution, a bag 307 for containing a salt-dextrose (SD) solution, a bag308 for containing dilution water (DW), and a bag 309 for containing abicarbonate (BC) solution that are positioned along the fluid flow patharrangement 300.

The bags 306, 307, 309 are pre-loaded with appropriate amounts of drychemicals that can be dissolved in water to produce the electrolytesolution, the salt-dextrose solution, and the bicarbonate solution. Eachbag 306, 307, 309 includes a nozzle that is designed to increase avelocity of a fluid flow entering the bag 306, 307, 309 and to createturbulence needed for adequate mixing and dissolution of the drychemicals in water.

Table 1 lists approximate capacities of the various fluid-containingcomponents of the fluid conditioning system 100.

TABLE 1 Capacities of fluid-containing components of the fluidconditioning system 100. Component Capacity (mL) Prime Tank (302) 8,000Primary Reservoir (304) 7,500 Secondary Reservoir (305) 4,500Electrolyte Bag (306) 500 Salt/Dextrose Bag (307) 160 Dilution Water Bag(308) 4,000 Bicarbonate Bag (309) 1,000

The three-way valves 202 of the fluid cassette 102 are indicated asV1-V7 in the fluid circuit 350. Each valve includes three fluid ports(a), (b), (c) by which a flow path in the valve can be adjusted. A valvemay be referred to as closed when two or three of its ports are closedand may be referred to as open when two or three of its ports are open.The valves include a prime valve V1, a dissolution valve V2, a bypassout valve V3, a bypass in valve V4, a BC/DW valve V5, an S/D/Electrolytevalve V6, and a fluid selector valve V7 The fluid lines 201 of the fluidcassette 102 will be referenced individually further below with respectto an operation of the fluid conditioning system 100. The high-capacitypumps 103 and the low-capacity pump 104 of the fluid conditioning system100 are indicated respectively as P1, P2 and P3, P4 in the fluid circuit350. The pumps include a cassette-in pump P1, a dialysate pump P2, aconductivity control pump P3, and an electrolyte/salt-dextrose pump P4.Table 2 lists approximate operational (e.g., fluid flow rate) ranges ofthe pumps P1-P4.

TABLE 2 Operational ranges of pumps of the fluid conditioning system100. Pump Operational Range (mL/min) P1 20-600 P2 20-600 P3 0.5-90  P40.5-90 

The heater assembly 151 and the ammonia sensor 165 of the fluidconditioning system 100 are respectively indicated as a heat exchangerHX and an ammonia sensor NH in the fluid circuit 350. The conductivitysensors 203 of the fluid cassette 102 are indicated as a conductivitysensor CT1 associated with a fluid temperature upstream of the heatexchanger HX and a conductivity sensor CT2 associated with a fluidtemperature downstream of the heat exchanger HX. In addition to having acapability to measure fluid conductivity, conductivity sensors CT1 andCT2 also have a capability to measure fluid temperature. Given thatconductivity changes with temperature, the temperatures measured by theconductivity sensors CT1 and CT2 may, in some implementations, be usedto correct conductivity values measured by the conductivity sensors CT1and CT2 to provide temperature-compensated conductivity measurements. Insome implementations, a fluid temperature measured by the conductivitysensor CT2 may also provide a safety check on a final temperature ofdialysate that exits the fluid conditioning system 100 to flow into thedialysis system 303. The temperature sensors 120 of the fluidconditioning system 100 are indicated as a cassette-in temperaturesensor T1 and a heat exchanger temperature sensor T2 in the fluidcircuit 350. The pressure transducers 119 of the fluid conditioningsystem 100 are indicated as pressure transducers PT1, PT2, PT3, and PT4in the fluid circuit 350.

The fluid conditioning system 100 can be operated in multiple stages tocooperate with the dialysis system 301 (e.g., with the dialyzer 337) forcarrying out a fluid conditioning cycle in which a dialysis treatment isadministered to a patient via the dialysis system 301. For example, thefluid conditioning cycle includes a priming stage, an infusion stage,and a treatment stage. The fluid conditioning cycle typically has atotal duration of about 135 min to about 300 min.

FIG. 20 illustrates operation of the fluid conditioning system 100during the priming stage, in which an initial volume of water is drawninto the fluid circuit 350 for subsequent creation of dialysate. At thebeginning of the priming stage, the prime tank 302 is filled to about7.6 L with water (e.g., tap water, bottled water, reverse osmosis water,distilled water, or drinking water) from a water source (e.g., acontainer 134 of water, shown in FIG. 19 ), pump P1 is turned on, andheat exchanger HX is turned on. The water is pumped by pump P1 from theprime tank 302 into a fluid line 310, through ports (a) and (c) of valveV1, into a fluid line 311, past temperature sensor T1, and into pump P1.At this stage of operation, pump P1 pumps water at a flow rate in arange of about 200 mL/min to about 600 mL/min, and heat exchanger HX ispowered to maintain a fluid temperature at a set point in a range ofabout 15° C. to about 42° C.

If temperature sensor T1 detects a water temperature of greater thanabout 42° C., then a message is displayed on the display screen 148 toadvise a user that the water temperature is too warm, valve V1 isclosed, and pump P1 is turned off to prevent additional water fromentering the fluid circuit 350. If temperature sensor T1 detects a watertemperature of less than or equal to about 42° C., then ports (a) and(c) of valve V1 remain open, and pump P1 pumps the water through a fluidline 312 into the sorbent cartridge 303, into a fluid line 313, pastammonia sensor NH, and into the primary reservoir 304. At this stage ofoperation, the sorbent cartridge 303 purifies the water circulating inthe fluid circuit 350, such that the water meets or exceeds waterquality standards for drinking water as set by the EnvironmentalProtection Agency (EPA) and water quality standards for hemodialysiswater as set by the Association for the Advancement of MedicalInstrumentation (AAMI) standard.

Once the primary reservoir 304 collects about 100 mL to about 500 mL ofwater, then pump P2 is turned on and pumps water into a fluid line 314,through pump P2, into a fluid line 315, past conductivity sensor CT1,and past the heat exchanger HX1, which heats the water in the fluid line315 to the set point temperature. Pump P2 is controlled to pump water ata flow rate that is about equal to the flow rate at which water ispumped by pump P1. Water moves from the fluid line 315 through ports (c)and (a) of valve V2, into a fluid line 316, through ports (b) and (a) ofvalve V7, into a fluid line 317, through ports (c) and (a) of valve V5,into a fluid line 318, and further into the bag 308 until the bag 308 isfilled to about 3.5 L to about 4.0 L with water (e.g., dilution water).

Next, ports (a) and (c) of valve V5 are closed, port (a) of valve V7 isclosed, and port (c) of valve V7 is opened such that the pump P2 pumpswater into a fluid line 319, through ports (c) and (a) of valve V6, intoa fluid line 320, and further into the bag 306 until the bag 306 isfilled to capacity with water to produce the electrolyte solution. Ports(a) and (c) of valve V6 are closed, port (c) of valve V7 is closed, port(a) of valve V7 is reopened, and ports (b) and (c) of valve V5 areopened. Pump P2 then pumps water into the fluid line 317, through ports(c) and (b) of valve V5, into a fluid line 321, and further into the bag309 until the bag 309 is filled to capacity with water to produce thebicarbonate solution.

At this point in the priming stage, the set point temperature of theheat exchanger HX is increased to a range of about 31° C. to about 39°C. (e.g., where 39° C. is the maximum temperature achievable by heatexchanger HX), and the flow rate of pump P2 is reduced to a value withina range of about 100 mL/min to about 300 mL/min to increase an exposuretime of the water within the heat exchanger HX for achieving the higherset point temperature. Ports (b) and (c) of valve V5 are closed, port(a) of valve V7 is closed, port (c) of valve V7 is opened, and ports (b)and (c) of valve V6 are opened. Accordingly, pump P2 pumps water intothe fluid line 319, though ports (c) and (b) of valve V6, into a fluidline 322, and further into the bag 307 until the bag 307 is filled tocapacity to produce the salt-dextrose solution. The higher set pointtemperature of heat exchanger HX facilitates dissolution of thesalt-dextrose substance with the water flowing into the bag 309. At thispoint during the fluid conditioning cycle, the priming stage concludes,the prime tank 302 has substantially emptied, the pumps P1, P2 areturned off and the infusion stage can begin. The priming stage typicallylasts a duration of about 10 min to about 30 min (e.g., about 20 min).

FIG. 21 illustrates operation of the fluid conditioning system 100during the infusion stage, in which bicarbonate, salt, and dextrose areadded to the water in the fluid circuit 350 to produce dialysate. Inparticular, bicarbonate, salt, and dextrose are added to the water in acontrolled manner (e.g., under flow rate control) until the salt anddextrose reach physiologically acceptable concentrations and until thebicarbonate yields a physiologically acceptable fluid conductivity andfluid pH. During the infusion stage, heat exchanger HX is powered tomaintain a fluid temperature at a set point in a range of about 35° C.to about 39° C.

At the beginning of the infusion stage, valve V7 is closed, port (a) ofvalve V2 closes, port (b) of valve V2 opens, ports (a) and (b) of bothvalves V3 and V4 open, port (b) of valve V1 opens, port (a) of valve V1closes, ports (b) and (c) of valve V6 remain open, and ports (b) and (c)of valve V5 open. Pumps P1, P2 immediately turn on to pump water at aflow rate in a range of about 300 mL/min to about 600 mL/min within thefluid circuit 350. At the same time, pumps P3 and P4 are turned on. PumpP3 pumps bicarbonate solution out of the bag 309 at a flow rate of about10 mL/min to about 100 mL/min, into the fluid line 317, through the pumpP3, and into the fluid line 314. Pump P4 pumps salt-dextrose solutionout of the bag 307 at a variable flow rate into the fluid line 319,through pump P4, and into the fluid line 314. The flow rate at which P4initially pumps fluid is in a range of about 1 mL/min to about 100mL/min. The flow rate is gradually stepped down by a factor of 2 atperiodic time increments of about 1 min. The flow rates of pumps P3 andP4 are set to completely add the infusion volume respectively of the BCsolution and the SD solution over a single revolution around the fluidcircuit 350. Accordingly, the flow rates of pumps P3 and P4 depend onthe flow rates of pumps P1 and P2 during the infusion stage. Forexample, if the flow rates of pumps P1 and P2 are set to 200 mL/min,then the flow rates of pumps P3 and P4 will be relatively slow.Conversely, if the flow rates of pumps P1 and P2 are set to 600 mL/min,then the flow rates of pumps P3 and P4 will be relatively fast.

Once the bag 307 empties of the salt-dextrose solution, port (b) ofvalve V6 closes, and port (a) of valve V6 opens to allow pump P4 to pumpthe electrolyte solution out of the bag 306 at a flow rate of about 0.5mL/min to about 5 mL/min into the fluid line 314. Once the electrolytesolution reaches valve V3, the infusion stage concludes, and thetreatment stage can begin. However, if the treatment stage does notbegin immediately, the fluid conditioning system 100 can be operated tocontinue to circulate dialysate around the fluid circuit 350 throughfluid lines 311, 312, 313, 314, 315, 323, 336, 326 or to allow thedialysate to remain static (e.g., without circulation) until thetreatment stage begins. The infusing stage typically lasts a duration ofabout 5 min to about 6 min.

FIG. 22 illustrates operation of the fluid conditioning system 100during the treatment stage, in which bicarbonate, salt, and dextrose areadded to the water in the fluid circuit 350 to produce dialysate. Thetreatment stage includes a first phase in which bicarbonate solution isused to regulate a conductivity of the dialysate and a second phase inwhich dilution water is used to regulate a conductivity of thedialysate. Pumps P1, P2 pump dialysate at a flow rate in a range ofabout 200 mL/min to about 600 mL/min. The set point temperature of heatexchanger HX is maintained at a physiologically acceptable temperaturein an acceptable range of about 35° C. to about 39° C. (e.g., about 37°C.), as specifically selected by a user of the fluid conditioning system100 to suit patient comfort. At any point during the treatment stage, ifthe dialysate fluid temperature measured at CT2 is outside of a range ofabout 35° C. to about 42° C., then the fluid conditioning system 100will enter a bypass mode in which dialysate will flow through fluid line336 to bypass flow through the dialysis system 301 via fluid lines 324,325. While the fluid conditioning system 100 is operating in the bypassmode, a message will be displayed on the display screen 148 indicatingthat the fluid temperature is too low or too high. The fluidconditioning system 100 will remain in bypass mode until the fluidtemperature stabilizes within the acceptable range.

During the first phase of the treatment stage, port (b) of valve V3 isclosed, port (c) of valve V3 is opened to allow pump P2 to pump “fresh”dialysate (e.g., cleaned, conditioned dialysate) through a fluid line324 and into the dialysis system 301, port (a) of valve V4 is closed,and port (c) of valve V4 is opened to allow pump P1 to pump “spent”dialysate (e.g., contaminated dialysate) through a fluid line 325 out ofthe dialysis system 301 and further into a fluid line 326. Accordingly,a bypass fluid line 336 that extends between valves V3, V4 is closed.During the treatment stage, spent dialysate is infused withultra-filtrate from the patient's blood within the dialysis system 301.The ultra-filtrate carries toxic substances, such as urea, all of thesmall water-soluble uremic toxins, and other toxic substances (e.g.,guanidosuccinic acid, methylguanidine, 1-methyladenosine,1-methylinosine, N2,N2-dimethylguanosine, pseudouridine, arab(in)itol,mannitol, α-N-acetylarginine, orotidine, oxalate, guanidine, erythritol,creatine, orotic acid, phenylacetylglutamine, creatinine, myoinositol,γ-guanidinobutyric acid, β-guanidinopropionic acid, symmetricdimethyl-arginine (SDMA), asymmetric dimethyl-arginine (ADMA), sorbitol,uridine, and xanthosine).

From the fluid line 326, the spent dialysate is pumped through ports (b)and (c) of valve V1, the fluid line 311, pump P1, the fluid line 312,and into the sorbent cartridge 303. Within the sorbent cartridge 303,the toxic substances are removed from (e.g., filtered out of) the spentdialysate to produce “regenerated” dialysate (e.g., cleaned,unconditioned dialysate) that flows out of the sorbent cartridge 303 andinto the fluid line 313, past the ammonia sensor NH, and into theprimary reservoir 304. In some cases, a volume of the regenerateddialysate within the primary reservoir 304 exceeds a capacity of theprimary reservoir 304 and therefore flows through a fluid line 327 intothe secondary reservoir 305, which remains in fluid communication withthe primary reservoir 304 throughout the treatment stage. Pump P2 pumpsregenerated dialysate out of the primary reservoir 304, into the fluidline 314, and into pump P2. While the regenerated dialysate exiting thesorbent cartridge 303 has been stripped of toxic substances that wereabsorbed from the patient's blood in the dialysis system 301, theregenerated dialysate must be further conditioned to meet acceptablephysiological properties before being circulated back into the dialyzer337 of the dialysis system 301 as fresh dialysate.

Accordingly, pump P4 continues to pump the electrolyte solution out ofthe bag 306 and into the fluid line 320, through ports (a) and (c) ofvalve V6, into an upper segment of the fluid line 319, through pump P4,and into the fluid line 314 at a flow rate that depends on (e.g., is afraction of) the flow rate at which pump P2 pumps dialysate. Thus, pumpsP2, P4 together form a closed pump control loop 332 that governs theflow rate at which pump P4 pumps the electrolyte solution, which is in arange of about 0.5 mL/min to about 5 mL/min. Furthermore, pump P3continues to pump either the bicarbonate solution out of the bag 309 orthe dilution water out of the bag 308, through port (c) of valve V5,into an upper segment of the fluid line 317, through pump P3, and intothe fluid line 314 to further condition the dialysate.

As the dialysate passes through pump P2 and conductivity sensor CT1, theconductivity sensor CT1 detects a conductivity of the dialysate. Basedon continuous measurements of the conductivity of the dialysate, eitherthe bicarbonate solution or the dilution water will be continuouslyselected for addition to the dialysate through port (c) of valve V5, andthe flow rate at which pump P3 pumps dialysate will be continuouslyadjusted to maintain a conductivity of the dialysate within aphysiologically acceptable range of 13.5 mS/cm to 14.2 mS/cm. Generally,as a difference between the measured conductivity and an acceptableconductivity increases, the flow rate at which the pump P3 pumps fluidincreases. Accordingly, as the difference between the measuredconductivity and the acceptable conductivity decreases, the flow rate atwhich the pump P3 pumps fluid decreases. In this manner, theconductivity meter CT1 and the pump P3 together form a closed pumpcontrol loop 331 that regulates a flow rate at which the pump P3 pumpsfluid. If the conductivity of the dialysate is too low during the firstphase of the treatment stage, then bicarbonate solution is infused intothe dialysate to raise the conductivity.

After passing the conductivity sensor CT1, the dialysate flows past theheat exchanger HX and temperature sensor T2. Based on a fluidtemperature detected by temperature sensor T2, a power level of the heatexchanger HX will be adjusted to maintain the temperature of thedialysate at the set point temperature of the heat exchanger HX. In thisway, temperature sensor T2 and heat exchanger HX form a closed heatercontrol loop 333. The dialysate flows from the fluid line 315 throughports (c) and (b) of valve V2 into the fluid line 323 and pastconductivity sensor CT2. As the dialysate passes conductivity sensorCT2, conductivity sensor CT2 performs a second check (e.g., downstreamof heat exchanger HX) to detect a conductivity of the dialysate.

If the conductivity of the dialysate is outside of the acceptable range(e.g., either too low or too high), but within a predetermined range(e.g., that is broader than the acceptable range), then a safety systemin electrical communication with the conductivity sensor will adjust aflow rate of infusion of the bicarbonate solution or the dilution waterto achieve a conductivity within the acceptable range. If theconductivity level of the dialysate is outside of the predeterminedphysiologically safe range, then, in some implementations, the fluidconditioning system 100 will attempt to restore the safe fluidparameters and continue the treatment. For example, valves V3 and V4will adjust to direct fluid through the bypass fluid line 336 and closefluid lines 324, 325 until a time at which the conductivity has againstably reached a physiologically safe range, at which time valves V3, V4will adjust to close the bypass fluid line 336 and direct fluid to andfrom the dialysis system 301 via fluid lines 324, 325. In someimplementations, a user may also be instructed to check that fluidlevels of the bicarbonate solution and the dilution water are non-zeroupon return of the conductivity to a physiologically safe range.

Over time, the sorbent cartridge 303 changes a composition of theregenerated dialysate exiting the sorbent cartridge 303 during the firstphase of the treatment stage (e.g., an early, initial phase in which thepatient's blood is initially circulated through the dialysis machine301). For example, during the first phase of the treatment stage, levelsof toxic substances within the spent dialysate are relatively high. Thesorbent cartridge 303 converts urea into ammonium and captures theammonium within one or more filtration layers within the sorbentcartridge 303 to remove the ammonium from the dialysate. While thefiltration layers capture the ammonium, the filtration layers releasesodium cations and other cations into the dialysate via cation exchange,which increases the conductivity and/or decreases the pH of theregenerated dialysate exiting the sorbent cartridge 303.

Over the course of the first phase of the treatment stage, spentdialysate entering the sorbent cartridge 303 contains fewer toxicsubstances (e.g., as uremic toxins are removed from the patient'sblood), and the sorbent cartridge 303 releases more sodium cations.Therefore, the conductivity of the dialysate exiting the sorbentcartridge 303 gradually increases over time. Once the conductivity ofthe dialysate reaches a predetermined value in a range of about 13.8mS/cm to about 14.0 mS/cm, the first phase of the treatment stage inwhich bicarbonate is used to regulate the conductivity of the dialysateconcludes, and the second phase of the treatment stage begins.

During the second (e.g., later, final) phase of the treatment stage,bicarbonate is no longer used to regulate (e.g., increase) theconductivity of the dialysate, and dilution water is the sole substanceat valve V5 that is used to regulate (e.g., decrease) the conductivityof the dialysate until the end of the treatment stage (e.g., the end ofthe second phase). Accordingly, port (b) of valve V5 is closed, whileport (a) of valve V5 is opened. If the conductivity of the dialysate istoo high during the second phase of the treatment stage, then dilutionwater is infused into the dialysate to lower the conductivity of thedialysate.

Over the course of the second phase of the treatment stage, an amount ofammonium captured in the sorbent cartridge 303 increases, such that acapacity of the sorbent cartridge 303 to absorb additional ammoniumgradually decreases, and a level of ammonia (e.g., generated by theammonium) within the regenerated dialysate eventually increases, oncethe capacity of the sorbent to adsorb ammonium is exhausted. The ammoniasensor NH detects the level of ammonia within the regenerated dialysateat a location downstream of the sorbent cartridge 303.

The treatment stage (e.g., including both the first and second phases)typically lasts a duration of about 120 min to about 300 min. Forexample, 240 minutes (e.g., 4 hours) is a standard duration thattypically achieves adequate treatment for the vast majority of patients.Furthermore, most treatment stages will end after four hours withoutreaching a threshold ammonium concentration of 2 mg/dL (e.g., withoutever approaching exhaustion of the filtering capabilities of the sorbentcartridge 303). The fluid conditioning system 100 will sound an audioalert signifying that the treatment completed successfully and that thepatient can disconnect himself or herself from the dialyzer 337.However, if the ammonium level in the dialysate (e.g., as detected bythe ammonia sensor NH) indicates that the sorbent cartridge 303 is nolonger absorbing enough ammonium from the spent dialysate to maintainthe ammonium level at or below an acceptable value of about 2 mg/dLprior to the standard treatment duration, then the treatment stage willconclude prematurely. Such conditions may occur occasionally for largerpatients that have very high blood urea nitrogen (BUN) levels.

Once the treatment stage concludes, the fluid circuit 350 can be drainedof spent dialysate, and the spent dialysate can be disposed of as waste.In some examples, the bags 306, 307, 308, 309 and the various fluidlines can be manually removed and discarded while still containingdialysate. In some examples, the patient may disconnect from thedialysis system 301 and drain the fluid lines 323, 326 to a wastereceptacle to empty the various components of the fluid conditioningsystem 100. In some examples, the fluid conditioning system 100 may beoperated to run either or both of pumps P1, P2 in a forward direction ora reverse direction to drain any of the bags 306, 307, 308, 309, thesorbent cartridge 303, the prime tank 302, the primary reservoir 304,and the secondary reservoir 305. In some examples, the fluidconditioning system 100 may be operated to run pumps P4 and P3 in aforward direction to drain the bags 306, 307 and 308, 309. In someexamples, such operation of pumps P4, P3 may be carried out based onreadings at conductivity meter CT1. For example, upon detection of asufficiently low threshold conductivity, the electrolyte bag 306 may beassumed to have been emptied, such that a next bag or fluid line can bedrained.

Throughout the fluid conditioning cycle, pressure transducers PT1, PT2,PT3, PT4 detect fluid pressures to regulate pump flow rates. Forexample, during all stages (e.g., the priming, infusion, and treatmentstages) of the fluid conditioning cycle, pressure transducer PT1 forms aclosed pump control loop 328 with pump P1 by detecting a fluid pressureof the dialysate within the fluid line 312 (e.g., located downstream ofpump P1) and providing a feedback signal to pump P1 indicative of thefluid pressure. Based on the fluid pressure of the dialysate, an angularspeed (e.g., an RPM level) of pump P1 is adjusted to maintain the flowrate within a desired range. During the treatment stage of the fluidconditioning cycle, pressure transducer PT4 forms an additional closedpump control loop 329 with pump P1 by detecting a fluid pressure of thedialysate exiting the dialysis system 301 (e.g., upstream of pump P1)and providing a forward signal to pump P1 indicative of the fluidpressure. Based on the fluid pressure of the dialysate, the angularspeed of pump P1 is adjusted to closely match the flow rate at pump P1with that of the dialysate exiting the dialysis system 301. Accordingly,the fluid pressure of the dialysate within the fluid line 312 (e.g.,downstream of pump P1) is at least in part affected by the fluidpressure of the dialysate exiting the dialysis system 301 (e.g.,upstream of pump P1).

Similarly, during all stages (e.g., the priming, infusion, and treatmentstages) of the fluid conditioning cycle, pressure transducer PT2 forms aclosed pump control loop 330 with pump P2 by detecting a fluid pressureof the dialysate within the fluid line 315 (e.g., located downstream ofpump P2) and providing a feedback signal to pump P2 indicative of thefluid pressure. Based on the fluid pressure of the dialysate, an angularspeed of pump P2 is adjusted to maintain the flow rate within a desiredrange. During the treatment stage of the fluid conditioning cycle, theflow rate at which pump P3 pumps fluid is regulated by a feedback signalfrom conductivity meter CT1 to form the pump control loop 331, and theflow rate at which pump P4 pumps the electrolyte solution is regulatedby a feedback signal from pump P2 to form the pump control loop 332, asdiscussed above.

During all stages of the fluid conditioning cycle, pressure transducersPT3 and PT4 detect operation of the dialyzer 337. If measurements atpressure transducers PT3 and PT4 indicate that there is no fluid flowthrough the dialyzer 337, then the fluid conditioning system 100 willenter the bypass mode to flow dialysate through fluid line 336 and toavoid delivering dialysate to the dialysis system 301 via fluid lines324, 325.

FIG. 23 provides a block diagram of the control system 161. The controlsystem 161 includes a processor 410, a memory 420, a storage device 430,and an input/output interface 440. In some embodiments, the controlsystem 161 includes more than one processor 410, memory 420, storagedevice 430, and/or input/output interface 440. Each of the components410, 420, 430, and 440 can be interconnected, for example, using asystem bus 450. The processor 410 is capable of processing instructionsfor execution within the control system 161. The processor 410 can be asingle-threaded processor, a multi-threaded processor, or a quantumcomputer. The processor 410 is capable of processing instructions storedin the memory 420 or on the storage device 430.

The memory 420 stores information within the control system 161. In someimplementations, the memory 420 is a computer-readable medium. Thememory 420 can, for example, be a volatile memory unit or a non-volatilememory unit. The storage device 430 is capable of providing mass storagefor the control system 139. In some implementations, the storage device430 is a non-transitory computer-readable medium. The storage device 430can include, for example, a hard disk device, an optical disk device, asolid-state drive, a flash drive, magnetic tape, or some other largecapacity storage device. The storage device 430 may alternatively be acloud storage device, e.g., a logical storage device including multiplephysical storage devices distributed on a network and accessed using anetwork.

The input/output interface 440 provides input/output operations for thecontrol system 161. In some implementations, the input/output interface440 includes one or more of network interface devices (e.g., an Ethernetcard), a serial communication device (e.g., an RS-232 10 port), and/or awireless interface device (e.g., an 802.11 card, a 3G wireless modem, ora 4G wireless modem). In some implementations, the input/output deviceincludes driver devices configured to receive input data and send outputdata to other input/output devices, e.g., keyboard, printer and displaydevices (e.g., the display screen 148). In some implementations, mobilecomputing devices, mobile communication devices, and other devices areused.

In some implementations, the input/output interface 440 includes atleast one analog-to-digital converter 441. An analog-to-digitalconverter converts analog signals to digital signals, e.g., digitalsignals suitable for processing by the processor 410. In someimplementations, one or more sensing elements are in communication withthe analog-to-digital converter 441, as will be discussed in more detailbelow.

In some implementations, the control system 161 is a microcontroller. Amicrocontroller is a device that contains multiple elements of acomputer system in a single electronics package. For example, the singleelectronics package could contain the processor 410, the memory 420, thestorage device 430, and input/output interfaces 440.

FIGS. 24 and 25 provide block diagrams of a hardware system 500 and asoftware system 600 of the fluid conditioning system 100 that areprovided by the control system 161. As shown in FIG. 24 , the hardwaresystem 500 is provided by a circuit board for generating GUIs fordisplay on the display screen 148 and one or more circuit boards 135 forcontrolling the electromechanical peripheral components of the fluidconditioning system 100, and the various electromechanical peripheralcomponents. The software system 600 can be broken down into an externalview 610, an application layer 620, and a driver layer 630. The externalview 610 includes user interfaces provided by the GUIs, lights, sounds,and debug ports. The application layer 620 includes business logic, andthe driver layer 630 is configured to implement peripheral-specific code(e.g., communication protocols and stepper motor drivers).

Although the example control system 161, the example hardware system500, and the example software system 600 have been describedrespectively in FIGS. 23-25 , implementations of the subject matter andthe functional operations described above can be implemented in othertypes of digital electronic circuitry, or in computer software,firmware, or hardware, including the structures disclosed in thisspecification and their structural equivalents, or in combinations ofone or more of them.

In some embodiments, the sorbent cartridge 303 of the fluid conditioningsystem 100 is equipped with a filter that can extend the usage life ofthe sorbent cartridge 303 from a single use for one dialysis treatmentto multiple uses for several dialysis treatments. FIGS. 26 and 27illustrate such an implementation in which a sorbent system 700 of thefluid conditioning system 100 includes the sorbent cartridge 303 and afilter 702 that is installed to an outlet 704 of the sorbent cartridge303 along the fluid circuit 350 (shown in FIG. 18 ). Accordingly, anyfluid flowing out of the sorbent cartridge 303 passes through the filter702 before reentering the fluid circuit 350. In some embodiments, thefilter 702 includes one or more membranes formed at least in part fromhigh performance thermoplastic fibers (e.g., polysulfone fibers). Insome embodiments, the filter 702 is an ultrapure filter. For example,the filter 702 may be designed to limit the microbial contamination offluid flowing through the filter 702 to below about 0.1 colony formingunits (CFU) per milliliter (mL) and to limit the level of bacterialendotoxins within the fluid to below about 0.03 international units (IU)per milliliter (mL). In some embodiments, the filter 702 may beinstalled to the sorbent cartridge 303 (e.g., and therefore incorporatedinto the fluid circuit 350) only when a dialysis treatment is not beingadministered to the patient to allow fluid to flow through the sorbentcartridge 303 at a relatively low flow rate between dialysis treatments,as will be discussed in more detail below.

The sorbent system 700 also includes the sorbent inlet line 312 leadingto an inlet 706 of the sorbent cartridge 303, the sorbent outlet line313 extending from the outlet 704 of the sorbent cartridge 303, a pump708 positioned along the sorbent outlet line 313, and the ammonia sensor165 and the ammonia detector 121 (indicated as NH in FIG. 18 )positioned along the sorbent outlet line 313. In some embodiments, theammonia sensor 165 and the ammonia detector 121 may communicatewirelessly with the dialysis system 301 (shown in FIG. 19 ). The sorbentsystem 700 additionally includes a bypass valve 710 located along thesorbent inlet line 312, a bypass valve 712 located along the sorbentoutlet line 313, a bypass fluid line 714 connecting the bypass valves704, 708, and a reusable power supply 716 with a backup battery. Thepump 708, ammonia sensor 165, ammonia detector 121, bypass valves 704,708, bypass fluid line 714, and power supply 716 together form areusable hardware module 720 of the sorbent system 700.

As shown in FIG. 28 , the sorbent cartridge 303 includes variousfunctional layers that together regenerate spent dialysate thatcirculates through the fluid circuit 350. For example, the sorbentcartridge 303 includes a first carbon layer 718, a urease layer 722, asecond carbon layer 724, a zirconium phosphate layer 726, zirconiumoxide layer 728, and a sodium bicarbonate layer 730. The carbon layers718, 724 include activated carbon for purifying the dialysate byadsorbing (e.g., binding) oxidants, chloramines, uric acid, otherorganic substances and by adsorbing middle molecules that may be presentin tap water or spent dialysate. The urease layer 722 decomposes theurea in the dialysate into ammonium and bicarbonate. The zirconiumphosphate layer 726 adsorbs ammonium (e.g., thereby removing ammoniumfrom the circulating dialysate) and several other compounds (e.g.,calcium, magnesium, potassium, metals, cationic metal complexes, andother cations) within the dialysate, while releasing sodium and hydrogeninto the dialysate. Finally, the sodium bicarbonate layer 730 releasessodium bicarbonate into the circulating dialysate. As long as the layersof the sorbent cartridge 303 have not been exhausted, dialysate exitingthe outlet 704 of the sorbent cartridge 303 will be in a substantiallyregenerated state.

Referring to FIGS. 18 and 27 , spent dialysate circulating through thefluid circuit 350 during a dialysis treatment cycle contains urea thathas diffused across the dialyzer 337 from the patient's blood, andammonium is produced within the dialysate as a result of ureadecomposition within the sorbent cartridge 303. As discussed above, thesorbent cartridge 303 is designed to remove ammonium as part of theprocess of regenerating the spent dialysate. Ammonium that is notremoved from the dialysate within the sorbent cartridge 303 can generateammonia within the circulating dialysate, and ammonia is toxic to thepatient above a certain threshold concentration (e.g., about 100 μg/dL).Therefore, the ammonia sensor 165 and detector 121 are positioneddownstream of the sorbent cartridge 303 (e.g., but upstream of theprimary reservoir 304, shown in FIG. 18 ) in order to identify ammoniumleakage in the dialysate and thereby protect the patient fromoverexposure to ammonia. If the ammonium level within the regenerateddialysate that exits the sorbent cartridge 303 exceeds an acceptablethreshold value during a dialysis treatment cycle, then the bypassvalves 704, 708 are controlled by the control system 161 (illustrated inFIG. 23 ) to close, thereby forcing dialysate through the bypass fluidline 714 to bypass the sorbent cartridge 303 as the dialysate circulatesthrough the fluid circuit 350.

The sorbent cartridge 303 is a heavy, disposable device that can bediscarded after each dialysis treatment performed using the fluidconditioning system 100 and replaced with a new sorbent cartridge 303when a next dialysis treatment is to be performed. In some examples,dialysis treatments may be performed at a frequency of anywhere betweenthree days per week and seven days per week. After a dialysis treatmentcycle has been completed with the fluid conditioning system 100 and thesorbent cartridge 303 is therefore not in use, bacteria often grow andaccumulate within the various layers of the sorbent cartridge 303 due toa state of stagnancy in which fluid is not circulating through thesorbent cartridge 303. For example, bacteria may begin to grow withinthe sorbent cartridge 303 after a brief period of stagnancy, andendotoxins derived from fragments of the bacteria may contaminatecirculating dialysate during a next dialysis treatment. Additionally,without a continuous flow of dialysate fluid through the layers of thesorbent cartridge 303 during the state of stagnancy, the layers cansolidify, thereby rendering the layers damaged or otherwise unsuitablefor adequately regenerating spent dialysate during a next dialysistreatment cycle.

Such damage to the layers of the sorbent cartridge 303 may be avoided bycontinuously circulating fluid through the fluid circuit 350 betweendialysis treatments. The fluid may be provided as tap water collected inthe prime tank 302. For example, referring to FIGS. 18 and 27 , asorbent preservation cycle may be carried out to circulate fluid in aloop sequentially through valve V1, fluid line 311, pump P1, sorbentinlet line 312 (e.g., equipped with bypass valve 710), sorbent cartridge303, filter 702, sorbent outlet line 313 (e.g., equipped with pump 708,ammonia sensor and detector NH, and bypass valve 712), primary reservoir304, fluid line 314, pump P2, fluid line 315 (e.g., equipped withconductivity sensor CT1, heat exchanger HX, temperature sensor T2, andpressure transducer P2), valve V2, fluid line 323 (e.g., equipped withconductivity sensor CT2 and valve V3), fluid line 336, valve V4, fluidline 326, and then returning to valve V1. Such fluid is unheated duringthe sorbent preservation cycle and therefore typically has a roomtemperature of about 15° C. to about 25° C.

Continuous fluid flow through the sorbent cartridge 303 prevents anysignificant amount of contaminants (e.g., bacteria, derivativeendotoxins, and other organisms) from growing or accumulating within thesorbent cartridge 303 and prevents accumulation of stagnant fluid withinthe sorbent cartridge 303. Furthermore, any small amounts of bacteria,other organisms, or other contaminants that may have been introducedinto the fluid at the sorbent cartridge 303 are trapped at the filter702 and thereby removed from the fluid as the fluid flows through thefilter 702. In this manner, the circulating fluid is cleaned (e.g.,filtered and purified) by the filter 702 as the fluid flows through thefluid circuit 350. Fluid may be circulated through the sorbent cartridge303 and through the filter 702 for a period of about 24 h to about 72 hbetween dialysis treatments. The filter 702 may be pre-installed to thesorbent cartridge 303, snapped into position by a user when the fluidconditioning system 100 is set up for treatment, or snapped intoposition by a user following completion of a dialysis treatment. Thefilter 702 has a light weight (e.g., having a mass of about 0.2 kg toabout 0.9 kg) and a small size (e.g., having a volume of about 200 cm³to about 400 cm³) that only marginally increase an overall footprint ofthe sorbent cartridge 303.

The pump 708 is a quiet, low-power pump (e.g., a peristaltic, piston,impeller, mushroom head, or other type low-power of pump) thatcirculates the fluid at a relatively slow flow rate of about 50 mL/minto about 150 mL/min to minimize power usage and therefore maximum systemefficiency during the sorbent preservation cycle. The power supply 716powers the hardware module 720 during the sorbent preservation cycle andincludes a backup battery that can power the hardware module 720 in theevent of a power failure. The filter 702 lasts at least as long as thesorbent cartridge 303 lasts and may last up to about 10 days, dependingon the size (e.g., the weight) of the sorbent cartridge 303, whichincreases after wetting. The sorbent cartridge 303 remains viable for aslong as the fluid circulates continuously and until the layers of thesorbent cartridge 303 are exhausted. Such exhaustion may be predictedahead of time with a calculation of a predetermined number of uses ofthe sorbent cartridge 303.

Circulating fluid through the filter 702 during the sorbent preservationcycle can extend the life of the sorbent cartridge 303 for use during apredetermined number of up to 8 dialysis treatment cycles over a periodof up to about 1.5 weeks, thereby avoiding costs and efforts (e.g.,lifting the sorbent cartridge 303) that would otherwise be associatedwith discarding and replacing a sorbent cartridge 303 each time adialysis treatment cycle would be performed during that time period.Once the sorbent cartridge 303 is finally exhausted, a removable,disposable module 732 of the sorbent system 700 (e.g., the sorbentcartridge 303, the filter 702, and the fluid lines 312, 313) may bedisconnected from the hardware module 720, discarded, and replaced for anext dialysis treatment. A new removable module 732 may be integratedwith the fluid circuit 350 using connectors with triggers and pins thatmaintain sterile connections along the fluid lines. Furthermore, thecontrol system 161 (illustrated in FIG. 23 ) of the dialysis system 301,electronically coupled to the fluid conditioning system 100 andtherefore the sorbent system 700, is operable to perform necessarysafety checks that examine pressure changes at the fluid lines 312, 313with respect to a timer 734 that tracks the usage life of the sorbentcartridge 303. In some embodiments, the timer 734 is integrated with thecontrol system 161. Once the timer 734 expires, the sorbent system 700and other components of the fluid conditioning system 100 will beprevented from operating until the disposable module 732 is replaced.

While the sorbent system 700 has been described and illustrated asincluding the pump 708 for circulating fluid during a sorbentpreservation cycle, in some embodiments, a sorbent system that isotherwise substantially similar in construction and function to thesorbent system 700 may not include the pump 708 and instead rely on thesynchronous operation of the pumps P1 and P2 in order to circulate fluidthrough the fluid circuit 350 during a sorbent preservation cycle.

While the sorbent system 700 has been described and illustrated with thefilter 702 resting atop the sorbent cartridge 303, in some embodiments,a sorbent system that is otherwise substantially similar in constructionand function to the sorbent system 700 may have a differentconfiguration for which the filter 702 is located at a differentposition within the fluid conditioning system 100, such as adjacent thefluid cassette 102 or at another position. At any position, an inlet ofthe filter 702 would be coupled to the outlet 702 of the sorbentcartridge 303.

While the sorbent system 700 has been described and illustrated as partof the fluid conditioning system 100, in some embodiments, the sorbentsystem 700 may be assembled with a different dialysis system (e.g., ahemodialysis system or a peritoneal dialysis system) to bestow aprolonged dialysate regeneration functionality to the system.

While the fluid conditioning system 100 has been described andillustrated as including the pressure transducers 119 (PT1, PT2, PT3,PT4) for regulating pump flow rates, in some embodiments, a fluidconditioning system that is otherwise similar in construction andfunction to the fluid conditioning system 100 may alternatively includeflow meters instead of pressure transducers for regulating pump flowrates. In some embodiments, a fluid conditioning system that isotherwise similar in construction and function to the fluid conditioningsystem 100 may not include pressure transducers or flow meters and mayinstead be RPM-controlled based on a detailed knowledge of the systemoperation to regulate pump flow rates.

While the fluid conditioning system 100 has been described andillustrated as including peristaltic pumps 103, 104 (P1, P2, P3, P4), insome embodiments, a fluid conditioning system that is otherwise similarin construction and function to the fluid conditioning system 100 mayalternatively include a different type of pump, such as an impellerpump, a linear displacement pump, positive displacement pump, or acentrifugal pump.

While the fluid conditioning system 100 has been described andillustrated as including one overflow reservoir (e.g., the secondaryreservoir 305), in some embodiments, a fluid conditioning system that isotherwise similar in construction and function to the fluid conditioningsystem 100 may include one or more additional overflow reservoirs. Forexample, in some embodiments, an additional reservoir may be connectedto the fluid circuit 350 upstream of pump P1 or downstream of pump P2.In some embodiments, an additional reservoir may have a capacitydifferent than that of either reservoir 304 or reservoir 305 or may havea zero volume capacity. In some embodiments, a reservoir may bepermanently connected to a drain.

While the heater bag 153 has been described and illustrated as beingarranged downstream of pump P2 of the fluid conditioning system 100, insome embodiments, a fluid conditioning system that is otherwise similarin construction and function to the fluid conditioning system 100 mayinclude a heater bag or other heating element that is arranged at adifferent location along the fluid circuit 350 in order to achieveoptimal temperature control of fluid flowing through the fluid circuit350. For example, in some embodiments, a heater bag may be positionedimmediately downstream of the sorbent cartridge 303 and may be poweredbased on signals from temperature sensor T1 to ensure that thetemperature of the dialysis fluid is not high enough to damage internalcomponents of the sorbent cartridge 303. In some embodiments, a heaterbag may be located along the fluid circuit 350 anywhere between valve V1and valve V2, as advantageous (e.g., to promote dissolution of the drychemicals in the supply bags 306, 307, 309).

While the fluid conditioning system 100 has been described as includingthree-way valves V1-V7, in some embodiments, a fluid conditioning systemthat is otherwise similar in construction and function to the fluidconditioning system 100 may alternatively include one or more two-wayvalves to achieve the fluid flow path scenarios discussed above.

While an operation of the fluid conditioning system 100 has beendescribed and illustrated with respect to certain flow rates, fluidvolumes, temperatures, pressures, and time periods, in some embodiments,the fluid conditioning system 100 may be operated to carry out a fluidconditioning cycle with one or more different flow rates, fluid volumes,temperatures, pressures, and time periods, while still functioning toadequately condition dialysate for use in a cooperating dialysis system.

Implementations of the subject matter described in this specificationcan be implemented as one or more computer program products, i.e., oneor more modules of computer program instructions encoded on a tangibleprogram carrier, for example a computer-readable medium, for executionby, or to control the operation of, a processing system. The computerreadable medium can be a machine readable storage device, a machinereadable storage substrate, a memory device, a composition of mattereffecting a machine readable propagated signal, or a combination of oneor more of them.

The term “computer system” may encompass all apparatus, devices, andmachines for processing data, including by way of example a programmableprocessor, a computer, or multiple processors or computers. A processingsystem can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A computer program (also known as a program, software, softwareapplication, script, executable logic, or code) can be written in anyform of programming language, including compiled or interpretedlanguages, or declarative or procedural languages, and it can bedeployed in any form, including as a standalone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

Computer readable media suitable for storing computer programinstructions and data include all forms of non-volatile or volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks ormagnetic tapes; magneto optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry. The components of the system can beinterconnected by any form or medium of digital data communication,e.g., a communication network. Examples of communication networksinclude a local area network (“LAN”) and a wide area network (“WAN”),e.g., the Internet.

Other embodiments are within the scope of the following claims.

What is claimed is:
 1. A method of preserving a sorbent device of adialysis system, the method comprising: after administering a firstdialysis treatment at the dialysis system and before administering asecond dialysis treatment at the dialysis system: circulating a fluidthrough the sorbent device to prevent matter within the sorbent devicefrom solidifying, and circulating the fluid through a filter coupled toan outlet of the sorbent device to remove contaminants from the fluid.2. The method of claim 1, further comprising circulating the fluidthrough the sorbent device and through the filter for a period of about24 hours to about 72 hours.
 3. The method of claim 1, wherein the fluidis unheated.
 4. The method of claim 3, wherein the fluid is at roomtemperature while the fluid is circulated, the room temperature beingabout 15° C. to about 25° C.
 5. The method of claim 1, furthercomprising circulating the fluid through the sorbent device and throughthe filter at a flow rate of about 50 mL/min to about 150 L/min.
 6. Themethod of claim 1, further comprising circulating the fluid using a pumppositioned downstream of the filter.
 7. The method of claim 6, furthercomprising powering the pump with a power supply.
 8. The method of claim7, wherein the power supply comprises a backup battery.
 9. The method ofclaim 1, further comprising regenerating spent dialysate using thesorbent device during the first dialysis treatment and during apredetermined number of additional dialysis treatments.
 10. The methodof claim 9, further comprising operating a timer of the dialysis systemto monitor a usage life of the sorbent device.
 11. The method of claim10, further comprising: determining that the sorbent device isexhausted; and preventing the dialysis system from operating afterdetermining that the sorbent device is exhausted.
 12. The method ofclaim 11, wherein the sorbent device and the filter are configured to bereplaced respectively with a new sorbent device and a new filter. 13.The method of claim 1, further comprising preventing dialysate frombecoming stagnant within the sorbent device.
 14. The method of claim 1,wherein the filter comprises an ultrapure filter.
 15. The method ofclaim 1, wherein the filter is disposed adjacent the sorbent device. 16.The method of claim 1, wherein the filter is disposed atop the sorbentdevice.
 17. The method of claim 1, further comprising administering thesecond dialysis treatment.
 18. The method of claim 17, furthercomprising: after administering the second dialysis treatment and beforeadministering a third dialysis treatment: circulating a fluid throughthe sorbent device to prevent matter within the sorbent device fromsolidifying, and circulating the fluid through the filter to removecontaminants from the fluid.
 19. The method of claim 1, wherein thecontaminants comprise one or both of bacteria and endotoxins.
 20. Themethod of claim 1, wherein the fluid comprises water.